The prior art describes a number of spray guns of the various types for spraying plural component materials in which the components are mixed prior to discharge or subsequent to discharge. For example, U.S. Pat. No. 3,837,757 shows an air actuator controlled by the trigger which operates the flow control ball valves. U.S. Pat. Nos. 3,806,030 and 3,752,398 disclose an apparatus for spraying plastics in which cleaning fluid is injected into the head by manually controlled valves after the spraying cycle. Air purge of the spraying apparatus is shown in U.S. Pat. No. 3,146,950. Another patent, namely U.S. Pat. No. 3,920,188 discloses a mode to disperse the polyurethane without the use of compressed air for atomizing or purging. U.S. Pat. No. 3,708,123 teaches about an airless spray apparatus permitting solvent and material flow into the spray apparatus involving a low pressure type operation using a novel mixing valve mechanism, which differs from the present invention. A rotary plug valve which is solenoid operated is shown in U.S. Pat. No. 2,659,628.
The description of a compressed air gun for spraying plural component coating materials is outlined in U.S. Pat. No. 3,837,023. This approach depends upon compressed air to atomize the mixed component materials ejected from the gun in a single mixing action, and to shape the spray pattern projected from the gun. During the spraying process the ejection orifice can not move axially or laterally from its cooperative association with the jets of air or the desired spray pattern will not be formed resulting in large droplets and/or uneven particle distribution. The orifice has to be stationary at all times, and the mixing depends upon the compressed air supply, which it cannot exceed. Additionally, U.S. Pat. No. 2,989,242, U.S. Pat. No. 3,245,661, U.S. Pat. No. 3,429,508, U.S. Pat. No. 3,795,364, U.S. Pat. No. 3,837,575 and U.S. Pat. No. 4,471,887 are all describing different functioning spray devices of different design.